Adaptable repairable and sealed limit switch

ABSTRACT

A limit switch or microswitch is described in which the switch or switches and the actuating means are entirely housed in a sealed, waterproof and airtight assembly. The switches are axially operable microswitches which are sealed in a switch housing which may be threadably engaged with the main assembly housing; thus facilitating easy replacement of switches. The actuating means is a reciprocating piston placed in a separate sealed housing member which also is in threaded engagement with the main assembly housing.

I United States Patent 13,566,053

[72] Inventor Ray A. Gause [56] References Cited L; Gragge, Tex. FOREIGNPATENTS i211 PP 8 7,33 264 762 6 1964 Netherlands 200 153 19 [22] FiledMay 23, 1969 i i 45] patented Feb. 23 1971 Primary Examn er Robert S.Macon [73] Assignee Gause Dynamics Corporation Assistant EmmmerHHohausel' Housmn Tex. Attorney-Cushman, Darby & Cushman [54] ADAPTABLEREPAIRABLE AND SEALED MIT ABSTRACT: A limit switch or microswitch isdescribed in SWITCH which the switch or switches and the actuating meansare entirely housed in a sealed, waterproof and airtight assembly.7Ch'ms2Drawmg Figs The switches are axially operable microswitches whichare [52] [1.8. CI 200/47, sealed in a switch housing which may bethreadably engaged 200/153 with the main assembly housing; thusfacilitating easy replace- [51] Int. Cl H02j l/l6 ment of switches. Theactuating means is a reciprocating [50] Field of Search 200/47, pistonplaced in a separate sealed housing member which also is in threadedengagement with the main assembly housing.

PATENIEU F B2319n 3; 566; 053

FIG. I

INVENTOR @flM RAY GAUSE AfToR ADAPTABLE REPAIRABLE AND SEALED LIMITSWITCH This invention relates to a limit switch using axially operablemicroswitches which are actuated by a reciprocally operating piston orplunger means.

An object of this invention is to provide a novel switch assembly whichwill permit the replacement of the holder in which the switch orswitches are mounted without requiring readjustment of the switchinstallation. In a preferred embodiment of this invention as describedhereinbelow this object is realized by mounting the switch in a switchhousing or holder which may be threadably engaged with a main assemblyhousing and in which the body of the switch housing or holder which maybe threadably engaged with a main assembly housing and in which the bodyof the switch housing is manufactured so that there is little variancebetween the lengths of like switch housings of the same manufacture.Therefore, the switch housing can be removed and replaced with a likemember without disturbing the basic installation or adjustment of theoverall switch assembly.

Another object of this invention is to provide a novel switch assemblywhich comprises three main component assemblies, each of which areeasily replaceable for maintenance purposes, and wherein the assembly issealed so that detrimental environmental conditions will not bedetrimental to the operation of the switch. Further, the sealed switchassembly constructed according to the principles of this inventionpermits installation in explosive environments because the smallinternal air volume and the sealed condition of the assembly will renderinternal and external explosions virtually impossible.

The foregoing and other objects and advantages of the invention willappear from the following description of a preferred embodimentillustrated in the accompanying drawings, wherein:

FIG. 1 is an expanded side cross-sectional view of a switch assemblyconstructed according to the principles of this invention showing thecomplete assembly as installed with a connector plug attached; and

FIG. 2 is a side elevation of the switch housing shown mounted in themain assembly housing in FIG. 1.

Referring to FIG. 1 the main assembly housing 1 is a hollow cylindricalmember having sharp V-threads in each end. Microswitches 17 are shownmounted in .a switch housing 2 which is threadably engaged with the mainassembly housing 1 and is shown as having a connector plug 19 connectedthereto in engagement with wires 21 extending from the microswitches 17.

At this point, reference is made to FIG. 2 for a structural descriptionof switch housing 2. FIG. 2 is an external side elevation of switchholder 2 with the switches 17 mounted therein and wires 21 extendingvertically from switches. Retaining pins 16 are provided extendingthrough the body of switch housing 2 to hold microswitches 17in place. Afriction lock is provided on the threads of the body of switch housing 2to hold it in place when threaded into assembly housing 1 and isespecially useful when the switch is subjected to heavy vibrations. Whenswitches 17 are inserted and pinned, by means of retaining pins 16, inhousing 2 and contact wires 21 are soldered on to switches 17, the axialdimension of switch housing 2 from a flange 32, at the upper end of theswitch housing, to end of the contact pin 30 is carefully checked. Inmanufacturing switch housings 2 this length dimension is maintainedwithin 10.003 inches during fabrication and assembly. By maintainingsuch dimensional consistency between switch housings, replacement ofswitch housings without further adjustment is readily facilitated.Further, such replacement may be accomplished without disturbing theinstallation or adjustment of the main switch assembly.

After establishing the proper length dimension, a potting compound,indicated as 20 in FIG. 1, is inserted around wires 21 over switches 17.The entire switch housing assembly LII shown in FIG. 2 afterconstruction in the foregoing manner may then be threadably insertedinto the main assembly housing 1 with a sealing or potting compound 15,see FIG. 1, installed in the mating area between housing 1 and theflange 32 of switch housing 2. Dual switches 17 are provided in thispreferred embodiment in order to provide a backup capability in theevent of a switch failure, but it must be noted that the principles ofthis invention are not limited in their application to a dual switchconstruction. Either switch may be selected to have a sufficient currentcapacity to perform the required function, and the size of wire used forwires 21 may be selected to carry current up to the maximum currentcapacity of the switch. As is conventional, the microswitches maycontain a center tap and may be wired for normally open or normallyclosed circuit functions permitting a variety of wiring configurations.Preferably the microswitches 17 are metal encapsulated for maximumprotection of the plastic switch body as well as providing environmentalprotection. The standard microswitch body may be modified by adding ametal shield and rubber diaphragm to yield the aforementionedenvironmental and assembly protection.

Referring back to FIG. 1, a piston housing 4 is threadably engaged withthe end of assembly housing 1 opposite the end in which switch housing 2is inserted. Piston housing 4 is hollow through the central portionthereof to allow the mounting therein of a piston member 5. Piston 5 isadapted to travel longitudinally through the axis of piston housing 4 inthe direction of contact pins 30. A piston guide 7, substantiallycylindrical in shape s inserted in the opening through piston housing 4between the inner surface of that opening and piston 5. 0- rings 12 and13 provide sealing between the guide 7 and piston housing 4 and theguide 7 and piston 5, respectively. A slipper seal 11 preferably made ofa self-lubricating material is provided and held pressurably againstpiston 5 also to facilitate motion of piston 5. A retaining ring 9 isplaced over piston guide 7 to hold the assembly in place. A compressionspring 18 in contact with piston guide 7 and a boss on piston 5 biasesthe piston away from switch contacts 30. A second piston guide 6 ismounted in the end of piston housing 4 away from the remainder of theassembly in the same manner as was piston guide 7. Another set ofO-rings l2 and 13 provide the necessary sealing of the areas between thepiston housing and the piston guide and the piston guide and the piston,respectively. Outside piston guide 6 is held in place by a-guide plate 8and a retaining ring 9.

After the entire piston housing assembly is inserted into the mainassembly housing 1, a potting compound 14 seals the interface betweenthe piston housing 4 and assembly housing I. The mating threads on thepiston housing 4 may also have a friction insert 10 to insure againstvibrations which may tend to loosen the thread joint. A button 3 ismounted on top of piston 5 in order to facilitate contact of the pistonwith contact pins 30 of switches 17.

In operation any force imparted to the exposed end of piston 5 will tendto move it in the direction of contact pin 30 of the switches 17. Theactuating force, which may be provided by a variety of means, such ashell cranks, cams or solenoids, must be sufficient to overcome thecompressive force of spring 18. It is to be noted that spring 18 may beselected to meet any of a variety of individual load requirements.Piston 5 will easily slide through slipper seals 11 which act as well toenhance the sealing effect of O-rings 13 which provide a compressiveforce behind the slipper seal 11. The O-rings 12 on the outside surfacesof piston guide 6 and 7, respectively, act to prevent moisture fromentering the switch cavity. The presence of piston guides 6 and 7insures that the motion of piston 5 will be only axial therebypreventing jamming or binding. The travel of piston 5 is unimpeded untilthe actuator button 3 makes contact with contact pins 30. From thispoint of initial contact switch 17 actuation requires only 0.03 inchesof travel of piston 5. Any additional travel of piston 5 will thenbottom-out on the piston housing 4. Any additional travel required couldbe handled by a standard microswitch over travel arm installed toactuate piston 5. As is apparent from the drawing, switches 17 areactuated simultaneously.

The material used for sealing or potting compounds 14, and will renderthe bottom and top joints of the switch assembly completely waterproof,and such compounds are available which will withstand temperatures ofup'to 800 F. The only possible leakage of air or liquids would have tobe around and past the two O-rings l2 and 13 and the slipper seals 11 oneach of the piston guides 6 and 7', and any such leakage is negligible.If desired, the entire assembly may be made of corrosion resistantmaterial to facilitate use in any environment. For use on aircraft whereweight is a critical factor, switch housing 2 and assembly housing 1 maybe fabricated from aluminum with the remainder of the parts being of thesame construction as described herein above.

To install a switch assembly constructed according to the principles ofthis invention assembly housing 1 need only be inserted in a dulledhole, e.g. five-eighths inches in diameter, and jam nuts 31 used tosecure it therein. Jam nuts 31 may be used as well to provide slightadjustments of the assembly, as when a new switch housing 2 isinstalled.

The preferred embodiment of my invention described hereinabove is onlyexemplary, and it will be apparent to those skilled in the art thatmodifications in the elements or their structural arrangement may bemade within the scope of the appended claims.

Iclaim:

l. A microswitch assembly comprising a hollow cylindrical housingmember, a microswitch housing threadably engaged into said assemblyhousing at one end thereof, first sealing means interposed between saidassembly housing and said microswitch housing preventing fluidcommunication between the interior of said assembly housing and theexterior thereof, at least one microswitch having an axially operablecontact pin, said microswitch being contained in a sealed manner withinsaid microswitch housing with said contact pin extending from saidmicroswitch housing into the interior of said assembly housing, a pistonhousing threadably engaged into said assembly housing at the other endthereof, second sealing means interposed between said assembly housingand said piston housing preventing fluid communication between theinterior of said assembly housing and the exterior thereof, piston meansmounted in said piston housing for axial motion therein and adapted atan end thereof interior of said assembly housing to abut and actuatesaid contact pin at the end of the axial travel of said piston mean sinto said assembly housing, and third sealing means interposed betweensaid piston means and said piston housing preventing fluid communicationbetween the interior of said assembly housing and the exterior thereofwhile allowing axial motion of said piston means in said piston housing.

2. The microswitch assembly defined in claim I wherein two microswitchesare contained and sealed in said microswitch housing in a side-by-siderelationship, one of said microswitches being adapted to operate in caseof failure of the other of said microswitches.

3. The microswitch assembly defined in claim 1 having in addition acompression spring means biasing said piston means in a direction awayfrom said contact pin of said switch and wherein said spring means isremovable for easy replacement with another spring having differentcompressibility, thereby easily adapting said assembly to differentuses.

4. The microswitch assembly defined in claim 1 wherein said microswitchhousing comprises a threaded outerbody adapted to be threadably engagedwith said assembly housing and wherein said microswitch is sealed insaid microswitch housing by a potting compound.

5. The microswitch assembly defined in claim 1 wherein said pistonhousing is a hollow, substantially cylindrical member and said pistonmeans comprises substantially solid shaft disposed at the center of saidhousing for reciprocal motion axially therethrough.

6. The microswitch assembly defined in claim 5 having In addition firstand second cylindrical piston guide means placed radially outwardly ofsaid piston means and radially inwardly of the interior surface of saidpiston housing for preventing eccentric motion of said piston means, oneof said guide means being placed on in an end of said piston housingadjacent the interior of said assembly housing and the other of saidguide means being placed in an end of said piston housing away from saidassembly housing and wherein said third sealing means comprises sealingrings interposed between each of said guide means and said piston meansand sealing rings inter posed between each of said guide means and theinterior surface of said piston housing.

7. The microswitch assembly defined in claim 6 wherein slipper seals areprovided between said sealing rings which are between said piston guidesand said piston in such a manner that said sealing rings exert acompressive force on said slipper seals.

1. A microswitch assembly comprising a hollow cylindrical housingmember, a microswitch housing threadably engaged into said assemblyhousing at one end thereof, first sealing means interposed between saidassembly housing and said microswitch housing preventing fluidcommunication between the interior of said assembly housing and theexterior thereof, at least one microswitch having an axially operablecontact pin, said microswitch being contained in a sealed manner withinsaid microswitch housing with said contact pin extending from saidmicroswitch housing into the interior of said assembly housing, a pistonhousing threadably engaged into said assembly housing at the other endthereof, second sealing means interposed between said assembly housingand said piston housing preventing fluid communication between theinterior of said assembly housing and the exterior thereof, piston meansmounted in said piston housing for axial motion therein and adapted atan end thereof interior of said assembly housing to abut and actuatesaid contact pin at the end of the axial travel of said piston meansinto said assembly housing, and third sealing means interposed betweensaid piston means and said Piston housing preventing fluid communicationbetween the interior of said assembly housing and the exterior thereofwhile allowing axial motion of said piston means in said piston housing.2. The microswitch assembly defined in claim 1 wherein two microswitchesare contained and sealed in said microswitch housing in a side-by-siderelationship, one of said microswitches being adapted to operate in caseof failure of the other of said microswitches.
 3. The microswitchassembly defined in claim 1 having in addition a compression springmeans biasing said piston means in a direction away from said contactpin of said switch and wherein said spring means is removable for easyreplacement with another spring having different compressibility,thereby easily adapting said assembly to different uses.
 4. Themicroswitch assembly defined in claim 1 wherein said microswitch housingcomprises a threaded outerbody adapted to be threadably engaged withsaid assembly housing and wherein said microswitch is sealed in saidmicroswitch housing by a potting compound.
 5. The microswitch assemblydefined in claim 1 wherein said piston housing is a hollow,substantially cylindrical member and said piston means comprisessubstantially solid shaft disposed at the center of said housing forreciprocal motion axially therethrough.
 6. The microswitch assemblydefined in claim 5 having in addition first and second cylindricalpiston guide means placed radially outwardly of said piston means andradially inwardly of the interior surface of said piston housing forpreventing eccentric motion of said piston means, one of said guidemeans being placed on in an end of said piston housing adjacent theinterior of said assembly housing and the other of said guide meansbeing placed in an end of said piston housing away from said assemblyhousing and wherein said third sealing means comprises sealing ringsinterposed between each of said guide means and said piston means andsealing rings interposed between each of said guide means and theinterior surface of said piston housing.
 7. The microswitch assemblydefined in claim 6 wherein slipper seals are provided between saidsealing rings which are between said piston guides and said piston insuch a manner that said sealing rings exert a compressive force on saidslipper seals.